The intake responses of three species of leaf-nosed Neotropical bats
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ORIGINAL PAPER
The intake responses of three species of leaf-nosed Neotropical bats Jorge Ayala-Berdon Æ Jorge E. Schondube Æ Kathryn E. Stoner Æ Nelly Rodriguez-Pen˜a Æ Carlos Martı´nez Del Rı´o
Received: 12 September 2007 / Revised: 5 December 2007 / Accepted: 6 December 2007 / Published online: 9 January 2008 Ó Springer-Verlag 2008
Abstract Flower-visiting bats encounter nectars that vary in both sugar composition and concentration. Because in the new world, the nectars of bat-pollinated flowers tend to be dominated by hexoses, we predicted that at equicaloric concentrations, bats would ingest higher volumes of hexoses than sucrose-containing nectars. We investigated the intake response of three species of Neotropical bats, Leptonycteris curasoae, Glossophaga soricina and Artibeus jamaicensis, to sugar solutions of varying concentrations (292, 438, 584, 730, 876, and 1,022 mmol L-1) consisting of either sucrose or 1:1 mixtures of glucose and fructose solutions. Bats did not show differences in their intake response to sucrose and 1:1 glucose–fructose solutions, indicating that digestion and absorption in bat intestines are designed under the principle of symmorphosis, in which no step is more limiting than the other. Our results also suggest that, on the basis of energy intake, bats should not prefer hexoses over sucrose. We used a mathematical
Communicated by G. Heldmaier. J. Ayala-Berdon J. E. Schondube (&) K. E. Stoner N. Rodriguez-Pen˜a Centro de Investigacio´nes en Ecosistemas, Universidad Nacional Auto´noma de Me´xico, Apartado Postal 27-3 (Xangari), 58089 Morelia, Michoaca´n, Me´xico e-mail: [email protected] J. Ayala-Berdon e-mail: [email protected] C. M. Del Rı´o Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071-3166, USA
model that uses the rate of sucrose hydrolysis measured in vitro and the small intestinal volume of bats to predict the rate of nectar intake as a function of sugar concentration. The model was a good predictor of the intake responses of L. curasoae and G. soricina, but not of A. jamaicensis. Keywords Bats Digestive modeling Intake response Nectar Sucrose hydrolysis Abbreviations DM Change in mass Csf Final concentration V0 Food intake Cs0 Initial concentration Km Michaelis–Menten constant Smax Rate of hydrolysis -rs Sucrose hydrolysis SI Sugar intake s Transit time G Volume of small intestine
Introduction The behavioural response of animals to foods that vary in energy concentration has been described in a variety of animals, ranging from insects (Slansky and Wheeler 1992; Josens et al. 1998) to large mammals (Spiegel 1973; Hansen et al. 1981). Typically, animals decrease intake as the concentration of assimilable energy in food increases (Montgomery and Bumgardt 1965; Slansky and Wheeler 1992). Castle and Wunder (1995) named the reciprocal relationship between intake and energy content ‘‘intake response’’.
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The intake response has been well studied in nectarfeeding birds (Collins 1981; Lo´pez-Calleja et al. 1997; McWhorter
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